The paint layer in a Japanese painting has a generally porous structure; an appropriate mathematical model based on an array of uniform close-packed spheres suggests that the glue medium covers only about half of the surface area of the pigment grains. Mounting the painting as a scroll keeps such a paint layer protected, makes the painting very compact while the scroll is rolled for storage, and avoids the chance of large stresses developing from humidity changes. When a scroll is unrolled and displayed, certain deformations, characterized as first-stage and second-stage deformation, may be observed. Deterioration of the materials results in embrittlement, which leads to the formation of lateral cracks and creases. Other kinds of damage result from careless handling, tying the rolled scroll too tightly or take the form of flaking of the paint layer. The recommended maximum period of exhibition of a scroll is about one month. The recommended relative humidity is 55-60%; below 50% should be avoided. -- ICCROM